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Tweaking Plants for Better Health

DNA prepared from each mutant plant is examined to identify mutant genes. Here, biologist Rae Ritchie collects leaf punchouts that will be used for DNA isolation.

Photo: Courtesy of the USDA

Genetically modified crops have received an official thumbs-down internationally, promises of feeding the world notwithstanding. But a new technology could get the same results without actual genetic modification.

It's called Tilling, or targeting induced local lesions in genomes, and it uses reverse genetics to pinpoint mutations that might enhance nutritional value or eliminate allergens. The technology thus far has not raised the hackles of environmental groups the way genetic modification has.

The controversy surrounding biotech foods often focuses on transgenics, the controversial technique that involves inserting genes from one species into another.

"The issue with transgenics is the capacity to bring in new genes that haven't been in that genome before," says Jane Rissler, a senior scientist at the Washington, D.C., Union of Concerned Scientists. "It's this power to combine genes from very different organisms that's causing concern."

Tilling, on the other hand, avoids these concerns because it relies solely on genes already in the plant.

Scientists at the USDA Agricultural Research Service's Crop Production and Pest Control research unit on the campus of Purdue University, have launched a Tilling project with the goal of making hypoallergenic soybeans. The researchers are creating as many mutations as they can in soybeans, then mining that information.

"It may be possible to identify mutants in the Tilling population that do not produce specific allergens," said Niels Nielsen, a geneticist working on the soybean project.

Soybeans are one of the top eight allergenic foods, along with peanuts. Food allergies affect 6 to 8 percent of children and 1 to 2 percent of adults. The U.S. government has mandated that all products with soy should be labeled as containing potential allergens in 2006.

Nielsen and his colleagues are also using Tilling to develop healthier soybean oil and higher-protein soybeans. They estimate that trans-fat-free nonhydrogenated soybean oil will be available in one year, while soybean oil that will rival olive oil for its monounsaturated fats is three years away.

Steven Henikoff and his colleagues at the Fred Hutchinson Cancer Research Center in Seattle first developed Tilling, a process that begins with soaking seeds in chemicals to induce mutations. Researchers then plant the seeds, and analyze genes from the mutated plant. They collect and store DNA samples containing mutations on a given gene.

Tilling can be used in a variety of plants. Researchers at Arcadia Biosciences in Davis, California, recently showed it could help develop an improved line of bread wheat.

The technology can also help scientists find previously unidentified mutations.

"By identifying mutants of genes whose function is unknown and studying them," Nielsen said, "it may be possible to deduce what they do."